ABSTRACT

The dynamic responses of monopiles induced by cyclic lateral loads, such as wind and wave, may change the lateral bearing behavior of the pile-soil system. A series of experiments were conducted in a wave- structure-soil interaction flume to identify the response features of monopiles under regular waves. The testing results indicate that the permanent displacement and cyclic amplitude of the fin pile is smaller than these of the monopile, and the aluminum monopile has the smallest response displacement. The wave load on the monopile with free-head is 4.99% lower than that on head-fixed monopile. The lateral stiffness of the monopile, fin pile and aluminum monopile, increases by 8.24%, 3.68% and 1.79%, respectively. The fin pile can be more efficient to resist the lateral load than the monopile with the same diameter.

INTRODUCTION

Monopiles are the one of the mostly-used types of the foundation for offshore marine structures, and their stability is affected by loadings in the harsh offshore environment. Because monopiles suffer from more complex loads compared with piles of onshore wind turbines, this effect which is important for engineering construction and maintenance is difficult to descript exactly in analytic method and needed to pay more attentions.

The dynamic responses of monopiles induced by cyclic lateral loads, such as wind and wave, could change the lateral stiffness of the pile- soil system (Poulos, 1988, Levy et al., 2009). Many model tests reported that the rotation angle and displacement of the pile increased with increasing numbers of load cycles because of the soils degradations (Rosquoët et al., 2007; Pablo, 2011), and the cross-section optimization was an available method to improve the response of piles (Peng et al., 2011; Bienen et al., 2012). It is worthwhile to note that the most of exist model tests assumed that the cyclic point load could represent the wave load (a distributed load), and the responses of monopiles under real wave actions was relatively less in prior literature.

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